Atlantic Hurricane Season Lies Dormant into Week Three

Erick forms in the eastern Pacific and forecast to strike southwest Mexico as a Category 2 hurricane by Thursday

It appears the Atlantic will stay storm free through week three of the hurricane season, with no development expected in the week ahead.

The pulse of storminess that moves eastward across the globe’s tropical band – a feature known as the Madden-Julian Oscillation or MJO that we previewed in week one of the hurricane season – helped to kick off a flurry of storm activity in the eastern Pacific. In just 9 days, four named storms, including one hurricane, formed.

Tropical Storm Erick became the 5^th named storm of the young eastern Pacific hurricane season early Tuesday and is forecast to strengthen into the basin’s second hurricane of 2025 on Wednesday.

As we discussed in Monday’s newsletter, activity in the eastern Pacific is running about a month ahead of schedule and never in the reliable record books (since around 1970) have we observed five named storms so early in the season out there.

Unfortunately for southwestern Mexico, Erick is expected to strengthen – likely rapidly – into a Category 2 hurricane and take aim at the area near or east of Acapulco by Thursday, a region of Mexico struck by several devastating hurricanes in recent years including John last September and Category 5 Otis in October 2023.

What’s on deck in the Atlantic

If we get through the week without a named storm in the Atlantic as expected, it’ll be the latest start to a hurricane season since 2014. Of course, as we’ve discussed in previous newsletters, a quiet start doesn’t imply the rest of the season will stay that way. The 2010, 2011, and the extremely active and destructive 2004 hurricane season went scoreless in the first three weeks of the season but ended as some of the most active seasons on record. The 2004 hurricane season was especially sneaky, with the first named storm not forming until August.

On average the first name storm in the Atlantic forms around the third week of the season.

The stormy side of the MJO weakened noticeably as it moved into the Atlantic over the weekend.

Phase diagram for the Madden Julian Oscillation or MJO. Each of the 8 pizza slices on the chart tells us where in the world the MJO is located, with slices 1, 2, and 3 being the Atlantic zone. The black line is where the MJO has already been and the nearby numbers are the dates of the month. In the plot above, for example, the MJO migrated from Indonesia and the Philippines (“Maritime Continent”) in late May to the eastern Pacific over the past 10 days. The circle at the middle shows us the strength of the MJO. The farther outside the circle, the stronger the MJO pulse. When the lines are inside the circle, it tells us the MJO is very weak or inactive. You can see how the black line dives into the circle as it crosses into phases 1, 2, and 3 over the past week, indicating a weak MJO on the Atlantic side. The MJO is forecast to return to the eastern Pacific and Atlantic by the first week of July. Credit: NWS Climate Prediction Center

The now subdued stormy branch will be quickly replaced by the suppressed back side of the MJO that should give us another few weeks of slumber in the deep tropics.

The next chance of widespread storminess returning to the tropical Atlantic won’t be until around the first week of July, when we begin to look a little farther out in the Atlantic for possible storm candidates.